1. Field of the Invention
This invention relates to a semiconductor device in which the surface portion of a semiconductor substrate having a dummy pattern formed separately from an integrated circuit pattern is annealed by radiation of light and a manufacturing method thereof.
2. Description of the Related Art
Conventionally, as a technique for putting an integrated circuit arranged on a semiconductor substrate into an electrically activated state, it is normal to establish and maintain the semiconductor substrate at a high temperature for several minutes by means of an annealing device having a heater. However, with recent miniaturization of integrated circuits, it becomes necessary to anneal only the surface portion of the semiconductor substrate and it becomes increasingly necessary to markedly reduce the annealing time in comparison with the conventional case.
Therefore, recently, the optical annealing technique for radiation light with high intensity for a short period to electrically activate an integrated circuit is proposed (T. Ito, et al., “10-15 nm Ultras shallow Junction Formation by Flash-Lamp Annealing”, Jpn. J. Appl. Phys., 2002, Vol. 41, 2394-2398). With this technique, the configuration is made to apply light from a light source to the surface of a semiconductor substrate arranged on a susceptor. The light radiation time is several tens of seconds or less and, as a result, the surface temperature of the semiconductor substrate instantly reaches a high temperature and only the surface portion is annealed.
As the light source, a light source of spike rapid thermal annealing (spike-RTA) that applies blackbody radiation light of approximately 3000K to 3500K for several seconds, flash lamp annealing (FLA) that applies light with a temperature of approximately 6500K for approximately 1 ms or laser spike annealing (LSA) that applies monochromatic light of wavelength approximately 10 μm for approximately 1 ms can be used.
In the optical annealing process, it is known that temperature irregularities occur on the semiconductor substrate. If the temperature irregularity is large, a variation in the threshold voltage of a circuit or crystal defects due to thermal stress will occur. Therefore, a method for forming an insulating film on the semiconductor substrate on which an integrated circuit pattern is formed and then forming a light absorption film that uniformly absorbs light on the insulating film to make the surface temperature uniform is proposed (Jp-A 2000-138177 (KOKAI)).
However, with the above type of method, it is not the semiconductor substrate itself (the semiconductor substrate including the integrated circuit pattern such as a gate pattern, element isolation pattern and the like) but the light absorption film formed on the insulating film. Therefore, time delay occurs from the time when the light absorption film is heated until the time the heat of the light absorption film is transmitted to the semiconductor substrate through the insulating film. The time delay becomes a factor that obstructs the short-time annealing process and, as a result, the circuit performance will be degraded.